The present invention relates to coupling devices which permit interconnecting a driving shaft to a driven shaft, such as a rod having an end stem of non-circular section and a shackle having a U section and, more particularly, a coupling device of this type which may be rapidly and reliably placed in position and in service.
In many technical fields, it is necessary to couple two shafts, for example a rod to an element such as a shackle, each associated with a shaft so as to connect the shafts in rotation.
This type of situation occurs, for example in the automobile industry, when the stem of a gear wheel of a steering box must be associated with the jaw of a universal joint connected to a shaft of a steering column.
A technique at present employed consists in providing that the shackle associated with the shaft to be connected to the gear wheel stem be connected to one of the jaws of the universal joint in such manner as to be pivotable about one of the axes of a spider element of the universal joint and arranging that this shackle caps a stem of non-circular section of the gear wheel. The stem, comprising a non-circular section of the rod, is trapped within the shackle, and held fast by fixing means.
These fixing means are usually formed by a screw-threaded pin provided on its periphery with cams, and which is mounted in the shackle and then clamped on the shackle by means of a nut. The pin is located in such manner that the cams of its periphery urges, into the inner end of the shackle, the stem comprising a non-circular section of the rod, and then the stem is clamped by screwing the nut on the end of the screw-threaded body of the screw which projects out of the shackle. If a lock-nut is used, it is conventional to screw the latter on the pin engaged in the shackle. After a few rotations of the nut, the pin encounters the locking part of the nut and the tightening torque increases. In continuing the screwing of the nut, the nut then drives the pin in rotation therewith and one of the cams of the pin comes in contact with the stem, which it then urges towards the inner end of the shackle. An additional screwing thereafter effects the locking of the assembly.
Although this technique is generally satisfactory, in service it is far from being reliable and far from being without drawbacks when assembling the parts.
As will be easily understood, if, when the shackle has been pivoted over the stem for capping the stem, the shaft carrying the universal joint turns through a semi-rotation before the fixing means have been placed in position, the shackle can be disengaged by pivoting in the opposite direction under the effect of gravity. The whole of the coupling operation must then be repeated.
If such a situation occurs upon assembly, however disagreeable this may be, it is without gravity.
However, if the fixing means become untightened and escapes from the latter, there is a danger of the latter becoming disengaged, as previously explained, and the initially coupled shafts are no longer coupled. This insidious situation is, as can be easily imagined, particularly dangerous if it concerns an automobile steering device.
Such an assembly is usually carried out in the engine compartment of a vehicle, where space is particularly restricted. In order to place the pin and nut in position, the operator must use both hands at the same time. This is particularly delicate if it is considered that, apart from the fact that the free space available to the operator is limited, access thereto is very often difficult.